Using transcriptome analysis to reveal the effects of bromoacetamide at drinking water ambient concentrations on the transformation of eDNA carrying ARGs

Abstract

Antibiotic resistance genes (ARGs) are frequently detected in drinking water. Transformation of extracellular antibiotic resistance genes (eARGs) is an important pathway for horizontal gene transfer, which facilitates the spread of ARGs among different species. Although most studies have pointed out that the presence of some common carbon-containing disinfection by-products, such as trihalomethanes, can increase the frequency of transformation by increasing the content of reactive oxygen species (ROS), nitrogen-containing disinfection by-products (N-DBPs), such as bromoacetamide (BAcAm), can also induce bacterial resistance to antibiotics by stimulating ROS. However, it is unclear whether such N-DBPs can similarly promote the transformation of ARGs in bacteria. In this study, the effect of BAcAm on the transformation of eDNA carrying ARGs was investigated, and found that DNA integration and repair (ruv, rec), efflux pumps (emr), and genes related to membrane proteins (bam, opm) were up-regulated in E. coli after addition of BAcAm. Furthermore, in addition to analyzing common functional genes, in terms of metabolic gene expression, which is usually overlooked, the genes related to amino acid biosynthesis (pot, arg, lys) were up-regulated while genes related to sulfur metabolism, which has a higher metabolic cost (thi, sssu) were down-regulated, which suggests that E. coli is able to effectively defend itself against the threat posed by BAcAm to its survival. In conclusion, the factors affecting the conversion of eDNA carrying ARGs into E. coli cells by BAcAm were suggested and elaborated that E. coli carrying ARGs can adapt to various unfavorable environments by regulating relevant metabolic mechanisms and survive in drinking water environment for a long period of time.